The present invention relates to communication apparatus and in particular, but not exclusively, to PCI Express interconnect apparatus.
In many computer environments, a fast and flexible interconnect system can be desirable to provide connectivity to devices capable of high levels of data throughput. In the fields of data transfer between devices in a computing environment, PCI Express (PCI-E) can be used to provide connectivity between a host and one or more client devices or endpoints. PCI Express is becoming a de-facto I/O interconnect for servers and desktop computers. PCI Express allows physical system decoupling (CPU<->I/O) through high-speed serial I/O. The PCI Express Base Specification 1.0 sets out behavior requirements of devices using the PCI Express interconnect standard. According to the Specification, PCI Express is a host to endpoint protocol where each endpoint connects to a host and is accessible by the host. PCI Express imposes a stringent tree structure relationship between I/O Devices and a Root Complex.
PCI device design can be engineering intensive and multi-function devices require additional effort to implement register sets per added function. Hardware needs to present a consistent model to software but aspects of a design such as the functions, devices, embedded bridges, etc., might not be determined early in the design and might need to change during development.